Description
The invention relates to a constant velocity universal joint for transmitting torque, having an outer joint part with outer ball tracks, an inner joint part with inner ball tracks, torque transmitting balls guided by pairs of outer and inner ball tracks positioned in corresponding meridian planes, and a ball cage which lodges the balls in circumferentially distributed windows and holds the balls in a common plane and guides the balls on to the angle-bisect-ing plane when the joint is articulated, with the center lines of the outer and inner ball tracks being composed of at least two differently curved portions adjoining one another.
Joints of this type are known as Rzeppa fixed joints (RF) or undercut-free fixed joints (UF). The latter are described in DE-PS 22 52 827. For a certain size of such joints, and especially as regards the axial length of such joints, there exists a mutual interdependence between the maximum articulation angle and the thickness of the shaft to be connected to the inner joint part. On the one hand, the articulation angle is limited in that the balls must be prevented from leaving the track ends, or, to be more precise, as far as edge loads at the track ends are concerned, it has to be ensured that there exists a sufficient safety distance between the point of contact of the ball in the track and the track end edge. Furthermore, the articulation angle is limited by the thickness of the connecting shaft which, upon articulation of the inner joint part, abuts against an inner cone of the outer joint part and thus prevents further articulation. It makes sense to adapt the thickness of the connecting shaft and the shape and position of the inner cone to one another in such a way that said abutment of the connecting shaft coincides with the safety distance between the point of contact of the ball and the track end edge.
Developments in automotive engineering are such that said constant velocity universal joints are expected to have an ever increasing performance, which means that with a predetermined available space and mass, the service life and functional scope have to be increased, or, vice versa, with a predetermined service and functional scope, space and mass have to be reduced.
With prior art joint designs, any improvements on the one side, for example in respect of the articulation angle, can only be achieved by shortening the service life and reducing the breaking strength.